More than 47,000 Europeans died from heat-related causes during 2023, the world’s hottest year on record, a new report in Nature Medicine has found.
But the number could have been much higher.
Without heat adaptation measures over the past two decades, the death toll for Europeans experiencing the same temperatures at the start of the 21st century could have been 80 percent higher, according to the new study. For people over 80 years old, the toll could have doubled.
Some of the measures include advances in health care, more widespread air-conditioning, and improved public information that kept people indoors and hydrated amid extreme temperatures.
“We need to consider climate change as a health issue,” said Elisa Gallo, the lead author of the study and a postdoctoral researcher at the Barcelona Institute for Global Health, a nonprofit research center. “We still have thousands of deaths caused by heat every year, so we still have to work a lot and we have to work faster.”
Counting deaths from extreme heat is difficult, in part because death certificates don’t always reflect the role of heat. The study used publicly available death records from 35 countries, provided by Eurostat, the statistics office of the European Union, and representing about 543 million Europeans.
The researchers used an epidemiological model to analyze the deaths alongside 2023 weekly temperature records to estimate what fraction of deaths could be attributable to heat.
“We’re quickly approaching the limits to what the human body can withstand,” said Jordan Clark, a senior policy associate at Duke University’s Heat Policy Innovation Hub who was not involved in the study. As the planet continues to warm, he said, “we’re racing against the clock.”
“We can’t adapt forever,” Dr. Clark said.
Heat waves are becoming more severe and prolonged as global temperatures increase. Ending our reliance on fossil fuels would be a core mitigation strategy, Dr. Clark said.
The past two decades have pushed people to modify their behaviors in response to heat, Dr. Gallo said. Other policy-level changes like improving urban planning, increasing green spaces, investing more in renewable energy and public transportation, and reducing greenhouse gas emissions could all contribute to adaptation.
“Adaptation has led to less deaths,” said Joan Ballester, associate research professor of climate and health at the Barcelona Institute and a co-author of the study. The term adaptation is meant very broadly, he added. It includes anything that reduces a group’s vulnerability to heat.
But pointing to the specific adaptation measures or policies that made the biggest differences is more difficult than estimating mortality, according to researchers.
In future studies, Dr. Gallo said she hoped to focus more on adaptations and differences between countries. The highest rates of heat-related deaths in the study occurred in countries that experienced the warmest temperatures over the longest periods of time, including high nighttime temperatures, like Bulgaria, Spain, Cyprus, Portugal, and Italy.
“It’s really important to have more studies on evaluations of what’s actually being done, that assess the evolution of adaptation,” said Francesca de’Donato, an environmental epidemiologist at the Lazio Regional Health Service in Rome.
One of the earliest forms of adaptation in Europe was a heat-related warning system that some countries, like Italy, adopted after an exceptionally warm summer in 2003 that contributed to more than 70,000 excess deaths across the continent. The country’s heat adaptation plan has been in place since 2004, based on guidance from the World Health Organization. The system directs medical and social service providers to check on people most at risk every few days when a warning is in effect. Registries indicate who is more vulnerable to heat based on factors like a chronic disease, age, socioeconomic status or whether someone lives alone.
A new website called Forecaster Health, created by the Barcelona Institute, provides an alert system that isolates subgroups that might be the most vulnerable by gender and age. In the future, Dr. Gallo said, those warnings could be even more specific to different illnesses like cardiac disease.
Dr. de’Donato’s region of Italy has been under a heat wave since late June. She said prolonged heat waves like the current one, in which temperatures fail to significantly drop for several days in a row, can have the greatest effects on human health.
Ashley Ward, director of the Heat Policy Innovation Hub at Duke University, said the study’s timing was critical as it came on the heels of a global call to act on extreme heat issued last month by the secretary general of the United Nations.
“Europe is really ahead of the U.S. on many of these kinds of activities, like heat governance and early warning systems,” Dr. Ward said. “The problem is growing faster than the data improvement is happening.”
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